Dielectric Fittings

Has anyone seen stainless used for Vacuum tubing? What kind of fitting must be used to make the transitions to the smaller copper tubing? The concerns are the fitting melting point, dissimilar metals, the dielectric fitting context is allowed to electrically isolate special equipment.

The larger tubing will be stainless and the smaller tubing will be copper. This is the only reference that I've found. The code regarding dissimilar metals touching is in regards to piping supports.

Reference: NFPA 99, 2015

5.1.10.9.2 Dielectric Fittings.Dielectric fittings that comply with the following shall be permitted only where required by the manufacturer of special medical equipment to electrically isolate the equipment from the system distribution piping:

(1) They shall be of brass or copper construction with an appropriate dielectric.

(2) They shall be permitted to be a union.

(3) They shall be clean for oxygen where used for medical gases and medical support gases.

5.1.10.2.1 Tubes for Vacuum.Piping for vacuum systems shall be constructed of any of the following: